Placenta Accreta Spectrum (PAS) is a pathological pregnancy condition characterized by abnormal invasion of the placental trophoblast into the uterine myometrium, sometimes penetrating the serosa or surrounding organs. ^{1, 2} The global incidence of PAS is increasing, largely associated with the rising rates of cesarean delivery and other uterine surgeries, which create decidual defects and elevate the risk of abnormal placental implantation. ^{3, 4} Previous uterine surgery in women with PAS increases the likelihood of peripartum hysterectomy. ⁵ Beyond these risk factors, vitamin D deficiency is suspected to contribute to PAS by affecting endometrial decidualization and trophoblast invasion. ⁶ Women with PAS are at high risk for obstetric complications, including postpartum hemorrhage, pelvic organ injury, coagulopathy, and even maternal death. ⁷ Early diagnosis and optimal management planning are therefore crucial to reduce morbidity and mortality associated with PAS. ⁸

Currently, imaging—particularly ultrasonography and magnetic resonance imaging (MRI)—remains the primary diagnostic method for PAS. Transvaginal and transabdominal ultrasonography are frequently used to detect specific signs of PAS, while MRI serves as an additional tool for cases difficult to identify with ultrasonography. ^{1, 2} However, both techniques have limitations, including equipment availability, operator expertise, and sensitivity in detecting early-stage PAS. ⁴ To improve early PAS detection, research has focused on identifying specific biomarkers for prenatal diagnosis. Key biomarkers showing potential include placental growth factor (PLGF), vascular endothelial growth factor (VEGF), and soluble fms-like tyrosine kinase-1 (sFLT-1), ⁷ which play important roles in angiogenesis and placental hypoxia, central mechanisms in PAS pathogenesis. ⁸

PLGF, a member of the VEGF family, is critical for regulating placental angiogenesis by promoting endothelial cell proliferation and differentiation, contributing to normal placental vascularization. ⁹ Studies show that maternal serum PLGF levels differ significantly between normal pregnancies and those complicated by PAS, with reduced levels in some PAS cases indicating impaired angiogenesis and abnormal trophoblast invasion. ¹⁰ VEGF is a key angiogenic factor that stimulates blood vessel formation and vascular permeability, inducing endothelial proliferation and enhancing adhesion molecule expression critical for vascular remodeling. ¹¹ In PAS, excessive VEGF expression may contribute to uncontrolled trophoblast invasion into the myometrium, leading to abnormal placental implantation. ⁷

The imbalance between angiogenic factors (VEGF, PLGF) and antiangiogenic factors (sFLT-1) is pivotal in preeclampsia pathogenesis and can also reflect placental hypoxia in PAS compared with normal pregnancy. ^{12, 13} Soluble fms-like tyrosine kinase-1 (sFLT-1), a natural VEGF antagonist, inhibits VEGF-receptor interaction, reducing angiogenesis. ¹ Elevated sFLT-1 levels are associated with angiogenic imbalance and placental hypoxia, commonly seen in PAS patients. ²

Histopathological analysis is essential for understanding PAS mechanisms. Histologically, PAS is characterized by the absence of a normal basal decidua layer, allowing direct trophoblast invasion into the myometrium. ⁴ Studies report increased chronic inflammation, abnormal vascular changes, and fibrosis in areas of abnormal placental invasion. ¹⁰ Immunohistochemistry confirms abnormal expression of angiogenic and inflammatory markers such as MMP-1, EGF, and VEGF-A. ¹¹ Recent research associates these biomarker expressions with the degree of placental invasion and PAS severity. ⁸ Therefore, this study aims to analyze the expression of angiogenic biomarkers PLGF, VEGF, and sFLT-1, as well as the histopathological characteristics of placental hypoxia in PAS patients compared with normal pregnancies.

This prospective case–control study was conducted at RSUP Dr. M. Djamil Padang between March, 2025 and November, 2025 to investigate maternal serum biomarkers (PlGF, VEGF, and sFlt-1) in placenta accreta spectrum (PAS) compared with normal pregnancy.

Table 1 shows the maternal characteristics in the case group (Acreta Placenta) and the control group (Normal Placenta). The analysis results indicate the demographic and clinical profiles that serve as a comparative basis for further analysis regarding the differences in biomarkers between mothers with acreta placenta and the control group. The distribution of maternal age between the two groups shows homogeneity, with a mean age of 30.77 ± 5.73 years in the Acreta Placenta group and 31.07 ± 5.88 years in the control group. Parity shows equal distribution with a mean of 1.36 ± 1.37 in the study group compared to 1.25 ± 1.06 in the control group. However, there is a noticeable difference in the history of abortion, which shows a higher tendency in the Acreta Placenta group (0.48 ± 0.73) compared to the control group (0.23 ± 0.52). The anthropometric profile represented through the body mass index shows homogeneity between the two groups (23.13 ± 3.33 kg/m ² vs 22.63 ± 3.03 kg/m ²).

Table 2 shows the results of the ultrasound examination indicating the variation in fetal growth between the two groups. The main biometric parameters include biparietal diameter (9.36 ± 0.84 cm vs 9.33 ± 0.74 cm), head circumference (32.63 ± 3.88 cm vs 33.20 ± 4.20 cm), abdominal circumference (32.26 ± 1.11 cm vs 31.96 ± 2.67 cm), femur length (7.23 ± 0.39 cm vs 7.23 ± 0.65 cm), and humerus length (6.29 ± 0.36 cm vs 6.30 ± 0.67 cm) which indicate the equivalence of fetal development in the case and control groups. The fetal hemodynamic parameters Systolic/Diastolic Umbilical Artery Ratio (DUAR) and Amniotic Fluid Index (AFI) also showed no significant disparity between the groups.

Table 3 shows that the perinatal results indicate a homogeneous outcome for birth weight between the two groups (2990.14 ± 391.34 grams vs 2996.11 ± 531.77 grams). The birth length also shows equality with a value of 46.77 ± 2.37 cm in the study group and 47.18 ± 4.11 cm in the control group.

Table 4 shows that maternal hemodynamic parameters indicate a stable mean arterial pressure (MAP) between the two groups (91.89 ± 7.28 mmHg vs 92.68 ± 13.14 mmHg). Biochemical profiles including liver function (SGOT, SGPT), renal function (urea, creatinine), and hematological parameters (hemoglobin) showed values within normal limits in both groups. However, significant variability was observed in the number of leukocytes and platelets in the Placenta Accreta group, which may reflect a heterogeneous physiological response to this pathological condition.

Table 5 shows significant differences in the expression of several angiogenesis biomarkers between the Placenta Accreta group and the normal pregnancy group. The analysis results indicate a characteristic pattern of angiogenesis dysregulation in the Placenta Accreta condition. For the biomarker sFlt-1, although it shows a lower median value in the Placenta Accreta group (191.310 pg/mL) compared to the normal group (258.015 pg/mL), it is not statistically significant (p = 0.102). For the biomarker AFP with a median value of 247.100 ng/mL in the study group compared to 256.350 ng/mL in the control group, it is also not statistically significant (p = 0.114). However, there is a significant decrease in two key angiogenesis biomarkers. The median value of PlGF in the Placenta Accreta group (3.825.660 pg/mL) is significantly lower than in the normal group (4.086.680 pg/mL) with p = 0.032. In the VEGF biomarker, the Placenta Accreta group showed a significantly lower median value (8.713.645 pg/mL) compared to the normal group (12.524.675 pg/mL) with p = 0.008. This indicates specific dysregulation in the angiogenesis pathway in Placenta Accreta, particularly in aspects mediated by PlGF and VEGF. The significant decrease in these two pro-angiogenic biomarkers indicates a disruption in the normal angiogenesis process that may contribute to the pathogenesis of Placenta Accreta. This selective dysregulation pattern highlights the complexity of angiogenesis regulation in placental pathology.

This study presents the profile of angiogenic biomarkers in Placenta Accreta Spectrum (PAS). The main findings showed a significant reduction in maternal serum levels of Vascular Endothelial Growth Factor (VEGF) and Placental Growth Factor (PlGF) in the PAS group compared to controls (p = 0.008 and p = 0.032, respectively), whereas levels of soluble Fms-like tyrosine kinase-1 (sFlt-1) and alpha-fetoprotein (AFP) exhibited a decreasing trend that was not statistically significant. The underlying mechanism of abnormal placental invasion in PAS is associated with decidual abnormalities, characterized by reduced, absent, or defective decidualization, which allows extravillous trophoblasts to penetrate deeper into maternal tissue. Molecular analyses indicate the involvement of two vascular formation mechanisms: vasculogenesis, the formation of new vessels from hemangiogenic cells via hemangioblastic differentiation regulated by VEGF and VEGFR, and angiogenesis, the growth of new branches from pre-existing vessels, in which PlGF plays a critical role. ¹⁴

The results indicate that maternal circulating VEGF levels were significantly lower in the PAS group compared with controls. This finding aligns with several previous studies. Uyanıkoğlu et al. (2018) reported significantly lower preoperative VEGF levels in placenta percreta (39.18 ± 11.98 pg/mL) compared to controls (85.87 ± 18.05 pg/mL, p < 0.001). Similarly, Schwickert et al. (2021) found significantly lower VEGF levels in the Abnormally Invasive Placenta group (285 pg/mL) compared to controls (391 pg/mL). In contrast, Faraji et al. reported that VEGF was not consistently a PAS marker, ¹⁵ showing a non-significant difference (p = 0.055), highlighting variability across studies. ^{15– 17}

The low VEGF levels in PAS cases may be explained by a decreased number of multinucleated giant cells (MNGCs) in the basal decidua, which are critical VEGF secretors during implantation. With fewer MNGCs, systemic VEGF production declines, resulting in lower free VEGF in maternal blood. Furthermore, invasive extravillous trophoblasts (iEVTs) that penetrate the basal layer show dual expression of vimentin and cytokeratin, reflecting epithelial–mesenchymal transition (EMT) similar to cancer cell invasion. VEGF appears to be used locally to enhance EVT motility and invasion rather than released into maternal circulation. This is supported by strong VEGF staining in local placental tissue, particularly at invasion sites and vascular lacunae, despite low maternal serum levels. ^{16, 18} Therefore, low maternal VEGF in PAS is not due to complete cessation of production but rather decreased MNGC sources and local utilization for abnormal trophoblast invasion.

Although sFlt-1 levels in this study did not differ significantly, the consistent decreasing trend aligns with most literature reporting lower sFlt-1 in PAS patients. A meta-analysis by Alzoub et al. (2022) confirmed significantly lower sFlt-1 in PAS compared to non-PAS controls (SMD = –7.76; 95% CI = –10.42 to –5.10; p < 0.0001). ¹⁹ Cai et al. similarly reported lower sFlt-1 levels in PAS (2075.57–2735.71 μg/L) compared with controls (2866.41 ± 226.77 μg/L, p = 0.001). ²⁰ Zhang et al. reported median sFlt-1 levels of 32.7 ng/mL in controls versus 12.8 ng/mL in PAS (p < 0.0001), and found sFlt-1 nearly three times lower in PAS than in non-PAS women. ¹⁴ Physiologically, sFlt-1 is a placenta-specific protein acting as a natural VEGF antagonist, irreversibly binding VEGF and suppressing its physiological function, thus exerting strong antiangiogenic activity. ²⁰ Low sFlt-1 in PAS is thought to be a secondary response to endometrium-myometrium injury, contributing to disease progression by removing the “brake” on angiogenesis. When VEGF increases while sFlt-1 decreases, this imbalance creates a highly pro-angiogenic and pro-invasive environment, promoting abnormal placental vessel formation and excessive trophoblast invasion into the myometrium, exacerbating PAS. ²⁰ Therefore, low sFlt-1 is not merely a marker but plays a causal role in PAS pathogenesis.

Similarly, PlGF levels were lower in the PAS group in this study. Uyanıkoğlu et al. reported lower PlGF in PAS (39.94 pg/mL) versus controls (76.65 pg/mL), ¹⁶ while Zhang et al. found higher PlGF in PAS (108 pg/mL) than controls (33 pg/mL), reflecting inter-study variability. ¹⁴ The present study supports the trend of PlGF reduction in PAS, indicating impaired placental angiogenesis. PAS primarily arises from a combination of placental dysfunction and a stressed microenvironment at abnormal implantation sites. Placentas developing over scar tissue receive high-flow blood from radial or arcuate arteries, triggering local oxidative stress and mechanical shear stress in the intervillous space. This stress disrupts normal syncytiotrophoblast function, suppressing PlGF synthesis and systemic release. Additionally, PlGF may be redirected locally to support invasive angiogenesis or suppressed by hypoxia and stress, resulting in lower maternal serum levels. ⁷ Variability between studies may be influenced by invasion severity (accreta, increta, percreta), gestational age at sampling, and biomarker assay methods.

In this study, AFP levels in the PAS group (24.7 ng/mL) did not differ significantly from controls (25.6 ng/mL, p = 0.114). Cai et al reported higher AFP in PAS (127.33–140.12 U/mL) than in controls (111.62 ± 14.25 U/mL). ²⁰ While some studies associate elevated AFP with PAS, possibly due to abnormal implantation, maternal-fetal interface damage, or increased placental vascular permeability, other factors such as maternal race, BMI, chronic illness, conception method, infection, medications, or non-pregnancy conditions (e.g., liver tumors, AFP-related genetic disorders) can affect AFP levels, limiting its specificity as a standalone marker. ²¹ These findings indicate that AFP is not a sensitive or specific single biomarker for PAS detection.

Overall, this study confirms that angiogenic biomarkers such as VEGF, sFlt-1, and PlGF play key roles in PAS pathogenesis, particularly through effects on placental angiogenesis and abnormal trophoblast invasion. In contrast, AFP did not differ significantly and is influenced by multiple maternal and non-pregnancy factors, precluding its use as a single sensitive or specific marker for PAS. These results underscore the need for a multifactorial approach, integrating biomarker analysis, clinical evaluation, and histopathological data for more accurate PAS detection. The study was limited by a small sample size due to strict inclusion criteria, resulting in a longer period to achieve the desired number of participants. Additionally, variability in medical record data required imputation for incomplete datasets to maintain analysis quality.

PAS is associated with lower levels of maternal serum PlGF and VEGF, as well as histopathological findings such as the absence or thinning of the decidua basalis, abnormal remodeling of spiral arteries, and excessive extravillous trophoblast invasion. These biomarkers have the potential to serve as additional diagnostic tools complementing imaging for the early detection of PAS.

The ethical implications of this study followed the provisions of the Declaration of Helsinki and were approved by the ethical committee of Universitas Andalas (Approval No. 536/UN.16.2/KEP-FK/2025). The participants approved and signed the informed consent. Participants hold the right to decline participation if they choose not to consent. The researcher assumes responsibility for covering all research-related expenses and associated costs.

Not applicable.